Use ApiPathString in app-server filesystem permission paths (#28367)

## Why

Clients running an app-server on one OS and an exec-server on another OS
need to be able to pass sandbox config to app-server that refers to
resources on the executor's foreign OS.

## What

`AbsolutePathBuf` can't represent these paths and we don't want users to
be exposed to `PathUri` yet, so this moves the public app-server API to
be expressed in terms of `ApiPathString`.

Stacked on #28165.

- change app-server v2 filesystem permission paths, including legacy
read/write roots, to `ApiPathString`
- localize API paths through `PathUri` when converting into the current
native core permission types
- make path-bearing permission conversions fallible and surface
localization failures instead of silently treating malformed grants as
ordinary denials
- propagate conversion failures through app-server and TUI approval
handling
- regenerate the app-server JSON and TypeScript schemas
- leave migration TODOs on native-path conversions so they can be
removed once core permission paths use `PathUri`

codex-rs/app-server-protocol/src/protocol/v2/item.rs

@@ -37,6 +37,7 @@ use serde::Serialize;
 use serde_json::Value as JsonValue;
 use serde_with::serde_as;
 use std::collections::HashMap;
+use std::io;
 use std::path::PathBuf;
 use ts_rs::TS;
 
@@ -687,9 +688,11 @@ impl From<CoreGuardianAssessmentAction> for GuardianApprovalReviewAction {
     }
 }
 
-impl From<GuardianApprovalReviewAction> for CoreGuardianAssessmentAction {
-    fn from(value: GuardianApprovalReviewAction) -> Self {
-        match value {
+impl TryFrom<GuardianApprovalReviewAction> for CoreGuardianAssessmentAction {
+    type Error = io::Error;
+
+    fn try_from(value: GuardianApprovalReviewAction) -> Result<Self, Self::Error> {
+        Ok(match value {
             GuardianApprovalReviewAction::Command {
                 source,
                 command,
@@ -742,9 +745,9 @@ impl From<GuardianApprovalReviewAction> for CoreGuardianAssessmentAction {
                 permissions,
             } => Self::RequestPermissions {
                 reason,
-                permissions: permissions.into(),
+                permissions: permissions.try_into()?,
             },
-        }
+        })
     }
 }